An inductive link for wireless power and data transmission generally includes a pair of radio-frequency (RF) coils, in which a primary (i.e. transmitter) coil supplies the energy in the form of a magnetic field, and a secondary (i.e. receiver) coil collects the energy from this field. For some applications the receiver coil will be positioned in an environment that requires the coil to be a very small size. Accordingly, the microfabrication of micro electromechanical systems (MEMS) that include such coils is important for applications in such varied fields as the biomedical, micro-fluidics and chemical analysis fields.
Miniaturized receiver coils useful for, e.g., transcutaneous energy transfer (TET), are generally characterized as having relatively low inductance. Accordingly, a dense magnetic field through this secondary coil is needed in order to transfer a sufficient amount of energy from the primary coil to the secondary coil. However, such a high field density might induce eddy currents in conductive materials resulting in undesired heating and damage in the materials surrounding the coil. In addition, a high input power source must be applied in the primary stage in order to generate a dense magnetic field.
The manufacture of RF coils generally includes mechanically winding metal wires into coils. However, such techniques are not suitable for the fabrication of coils capable of transferring sufficient power in the presence of less dense magnetic field. Accordingly, precise and reproducible mechanisms for microfabricating devices that concentrate the magnetic flux of a secondary coil to achieve higher power densities and efficiencies are needed.